RKO Pictures essentially ceased to be around the 50’s by being bought by Desilu. However, it is still around: Dina Merril and Ted Harley own now what is left of RKO.
Now to the Disney question:
Early Disney movies, like Snow White or Dumbo, were released with the RKO logo at the beginning of the movies, since Disney still had no distribution system. AFAICR RKO originally distributed Snow White, but it eventually ended up a Disney title only; however, in new releases (I have to take care of my relative’s kids sometimes) the RKO original title appears! Now why Disney, that is so defensive of their trademarks, not removing (or now adding?) the RKO logo?
I have to ask too: What is the deal now with RKO pictures?
A list of all of the animated films ever released in the United States lists all films through Peter Pan as being released by “RKO-Disney.” I can also find reference to the RKO “thunderbolt” logo (“Distributed by RKO RADIO PICTURES”) appearing on Disney films until 1953 (Sometimes later replaced with a “Buena Vista Distribution” logo), and I have also seen the words “Distributed by RKO Radio Pictures Inc.” on the title and end cards of Disney cartoons (the titles which begin with the familiar “sunbeam” picture of the star character’s smiling face).
Obviously, the RKO-Disney partnership lasted longer than you originally thought.